It is well known that bisphenols, such as bisphenol-A, can be obtained by the interaction of phenol with acetone or other ketones in the presence of acidic condensing agents. These processes, however, have yielded products contaminated with a large number of by-products, such as chromans, spiro compounds, linear or cyclic dimers of isopropenylphenols and compounds of more complex structures which are generally unsuitable for technical operations without extensive and difficult time--and energy--consuming purification steps.
It has now been discovered that excellent yields of highly pure bisphenols can be obtained by substituting for the acetone or other ketone reactant a compound containing as an essential structural feature, an arrangement of carbon and oxygen atoms of any of the following structural formulae ##STR3##
It has been discovered that the reaction is very fast near room temperature (.about.30.degree. C.), and, except for the o,p' isomer (with phenol as the reactant) only very small amounts of contaminants are formed when "p,p'-bisphenol-A" is the desired product. In any event, the by-products, including the o,p' isomer, are easily removed by a simple slurrying of the separated solids with methylene chloride.